The invention relates to aquarium filters providing improved mechanical water filtration without accelerating the rate of clogging. The present invention also relates to methods of using such filters.
Aquarium filter systems which continuously circulate water from an aquarium, through a filter medium and, then, back to the aquarium are well known in the art. One such type of aquarium filter system is represented by the external-type system which employs a small container comprising a filter mounted on the side of the aquarium. The water from the aquarium is drawn by means of a water pump, it flows through filter medium in the container and is then returned to the aquarium. The filter medium is usually in the form of elements of activated carbon or charcoal and fluffy masses of synthetic resin fibers.
Examples of external-type filter systems can be found in U.S. Pat. No. 3,513,978 to Newsteder and U.S. Pat. No. 3,525,435 to Conner, both of which are herein incorporated by reference in their entirety.
The Newsteder system uses two separate compartments, each filled with a different filtering substance (i.e., fibrous filtering material and charcoal respectively). The water flows through the fibrous material and then through the charcoal before going back to the aquarium. In this type of filter, however, the compartment holding the charcoal must have very restricted openings to prevent any charcoal from passing through openings into the aquarium.
The Conner filter uses a perforated top with a dependent filter bag that is filled with charcoal. The flow of the water is down through the top, out through the bag walls and then back into the tank. The Conner filter is wholly disposable. The filter, however, lacks a mechanism for mechanically or physically filtering water prior to passing through the charcoal. Consequently, the filter allows waste particles to enter the interior space of the filter and, thereby, reduce the effectiveness of the charcoal. Specifically, particulate matter can block (or occlude) the surface of adsorbents like charcoal and activated carbon and, thus, reduce their capacity to surface adsorb dissolved gases and toxins.
Another type of aquarium filter is the internal or underwater filter. A container is provided which includes a filter medium such as activated carbon or charcoal and a fluffy mass of synthetic resin fibers. An air lift is provided, extending vertically up from the container, and air is pumped down into the base of the air lift from an external air pump. The air rises which, in turn, induces water flow into the container, such that the water passes through the filter medium and, then returns back to the aquarium.
In aquarium filtration, the filter medium provides various types of filtration activity. As the water flows through a porous wall, mechanical filtration of the water occurs with the walls acting as a sieve, retaining the solid contaminants. The mechanical filtering capability of this xe2x80x9csieve-typexe2x80x9d mechanism increases for finer contaminants as the surface area of the porous wall increases and the pore size of the openings or interstices decrease. Increasing the density of the porous wall results in improved trapping of smaller particles. Such increases in the surface area of the porous wall, however, also results in accelerated clogging rates of the porous wall. Therefore, a need exists for filter cartridges providing mechanical filtration using high density (or, high surface area) porous walls to improve the filtration of finer contaminants without a corresponding acceleration in the clogging rate of the filter cartridge as a whole.
The present inventors have discovered that filter cartridges incorporating dual density filters, comprising a low-density (surface area) in-flow porous wall and a high-density (surface area) out-flow porous wall, provide improved mechanical filtration without accelerating clogging.
Accordingly one aspect of the present invention is to provide improved filter cartridges.
A further aspect of the present invention is to provide filter cartridges which improve mechanical filtration without accelerating the clogging of the filter cartridge.
A still further aspect of the present invention is to provide filter cartridges comprising a plurality of filter walls produced from porous materials, with each wall varying in density or surface area such that the density or surface area of the filter walls increases in the direction of water flow.
These and other advantages are accomplished by the present invention as will be further detailed in the following description.
The present invention relates to water filter articles, comprising:
a.) a first porous filter wall for filtering liquid flowing into the filter article; and
b.) a second porous filter wall for filtering liquid flowing out of the filter article
wherein the density or surface area of the first porous filter wall is less than the density or surface area of the second porous filter wall. Methods of using the disclosed filter are also described.
Frame
The frame is constructed with laterally projecting separators. The separators extend across the filter cartridge and have a narrow dimension transverse to the flow of the aquarium water there across so as to cause only minor restriction to the flow. The separators have a broad dimension parallel to the direction of flow, and can serve to space apart the filter walls. The surface of the frame is also textured to provide increased available surface area. This increased surface area additionally provides a support media for growing organisms active in biological filtration.
The frame also provides an internal structure for the plurality of filter walls described herein. Accordingly, water can be, first, circulated through an in-flow filter wall on one side of the filter cartridge, next, through the interior space of the filter cartridge and, finally, exit through the out-flow filter wall on the opposite side of the filter cartridge. The in-flow filter wall of the filter cartridge captures and retains large contaminants from the water before it reaches any optional chemical filtration material, such as activated carbon, typically disposed within the filter cartridge while the out-flow filter wall filters out smaller contaminants.
Frames suitable for use herein are described in detail in U.S. Pat. No. 5,053,125 to Willinger et al., herein incorporated by reference in its entirety.
Filter Walls
The filter cartridges of the present invention comprise at least two filter walls. The filter walls of the present invention are, preferably, comprised of a water permeable porous, filter membrane material. The density or surface area of the filter membrane material differs from one filter wall to the next, with the first filter wall (or the filter wall receiving incoming water) having a lower density or surface area than the second filter wall. Water exiting the lower density or first filter wall will contain fewer particulates, thus, reducing the surface loading on the carbon and enhancing its effective life. The higher density out-flow or second filter wall, in turn, filters the finer waste particulates as well as prevent carbon from being carried out of the filter by the water flow into the aquarium.
The membrane can be formed of an open web of closely spaced and randomly disposed fibrous or filamentary substances and/or polymeric materials which form a 3-dimensional matrix and provides for numerous interstices or pores defining water passages. Any filter material or substance suitable for forming such matrices, interstices or pores can be used to form the filter walls of the present invention. Passage of the water through the interstices in the membrane material causes mechanical filtration of the water by the filter walls retaining solid waste and other contaminants. Increasing the density or surface area of the porous material increases the mechanical filtration capability of the filter wall for finer particulate contaminants.
Suitable porous membrane materials include a variety of water insoluble substrate materials. Particularly useful as the porous materials in the present invention are reticulated foams, synthetic resin fibers, nonwoven fibrous materials and mixtures thereof.
Nonwoven Fibrous Material:
A detailed discussion of nonwoven fibrous materials can be found in Riedel, xe2x80x9cNonwoven Bonding Methods and Materials,xe2x80x9d Nonwoven World (1987); The Encyclopedia Americana, vol. 11, pp. 147-153, vol. 21, pp. 376-383, and vol. 26, pp. 566-581 (1984); U.S. Pat. No. 4,891,227, to Thaman et al., issued Jan. 2, 1990; and U.S. Pat. No. 4,891,228 and U.S. Pat. No. 5,686,088 to Mitra et al., issued Nov. 11, 1997; U.S. Pat. No. 5,674,591; James et al; issued Oct. 7, 1997; all of which are herein incorporated by reference in their entirety. The term xe2x80x9cdensityxe2x80x9d, as used herein in connection with nonwoven fibrous materials, means the number of pores or interstices per unit measure (i.e., volume or length) of a porous wall such that higher density porous walls have more pores of various sizes, and preferably smaller pores, per unit volume than lower density porous walls.
Preferably, the nonwoven fabric material of the filter walls has a weight per unit length ranging from 2 (or about 2) oz per linear yard to 15 (or about 15) oz per linear yard, more preferably from 2 (or about 2) oz to 5 (or about 5) oz per linear yard and most preferably 2.5 (or about 2.5) oz to 3.75 (or about 3.75) oz.
The nonwoven fibrous material making up the in-flow (first) and out-flow (or, second) filter walls are distinguished by the fiber deniers used to form them. Preferably, the nonwoven fibrous materials making up the first (or in-flow) filter wall comprises a blend of fiber deniers ranging from 4 (or about 4) to 20 (or about 20) denier, and between 1 (or about 1) and 4 (or about 4) inches long, and more preferably from 6 (or about 6) to 15 (or about 15) denier with lengths between 2 (or about 2) and 3 (or about 3) inches, resulting in a xe2x80x9clowxe2x80x9d or xe2x80x9clowerxe2x80x9d pore density filter walls.
In contrast, the nonwoven fibrous materials making up the second (or outflow) filter wall comprises a blend of fiber deniers ranging from 1 (or about 1) to 8 (or about 8) denier, and between 1 (or about 1) and 4 (or about 4) inches long, and more preferably from 2 (or about 2) to 6 (or about 6) denier with lengths between 1 (or about 1) and 2 (or about 2) inches, resulting in pore densities xe2x80x9chigherxe2x80x9d than those of the first or in-flow filter walls, provided that the blend of fiber deniers for the first filter wall is less than the blend of fiber deniers.
The blend of fibers in the first wall will have a significant portion of longer and larger denier fibers than the second wall.
Polymeric Foam Materials
Also useful herein are polymeric foam materials. Useful polymeric foams materials include those polymeric substances conventionally used in preparing polymer foams such as polyurethanes, including a polyether-polyurethane foam or a polyester polyurethane foam;
polyesters; olefin polymers, such as a polypropylene or polyethylene; vinyl and styrene polymers such as polyvinylchloride, and polyamides. Examples of commercially available preferred organic polymer substrates include polyurethane foams marketed by Foamex International, Inc., including polyether-polyurethane foams, and polyester polyurethane foams as well as foams marketed by Recticel S.A. Preferably, the polymer foams are reticulated foams.
In the case of polymer foams (e.g., reticulated foams), density, as used herein in connection with polymer foams, means to pores per inch (ppi) associated with a particular foam. Higher or high density polymer foam filter walls preferably have densities of from 20 (or about 20) to 45 (or about) 45 ppi, more preferably from 25 (or about 25) to 30 (or about 30) ppi while low or lower density polymer foam filter walls preferably have densities of from 10 (or about 10) to 30 (or about 25) ppi, more preferably from 15 (or about 15) to 20 (or about 20) ppi.
The filter cartridge can be inserted in an external or an internal filter apparatus such as a corner or bottom filter device. The filter walls can be in the form of an envelope, covering the rigid or semi-rigid frame and facilitating the sealing of the filter cartridge to the filtering apparatus along the interface between the two elements. This eliminates the need for a tight tolerance matching between the filter cartridge and the filter device and also prevents breaking or scratching the wall of the filter device.
Optionally, the filter cartridge of the present invention can be designed to hold particulate filter materials such as charcoal, activated carbon or mixtures thereof.
The filter cartridge can be used as a filtering device by itself by causing a flow of the water through the filter cartridge.